Why Are My Tree Leaves Turning Brown or Yellow? Causes & Fixes

Seasonal Causes vs. Disease

Not all leaf discoloration is cause for alarm. Fall color change is the most obvious seasonal cause, but trees can also show yellowing in spring due to delayed leaf emergence or cool, wet conditions. Inner needle drop on conifers like white pines and arborvitae is a normal autumn process where the oldest needles turn yellow or brown and fall, while the current year's needles remain green.

However, leaf discoloration during peak growing season (June through August in most regions) is more concerning. Uniform yellowing across the tree suggests a systemic problem like root damage, nutrient deficiency, or vascular disease. Patchy or spotted discoloration often points to a foliar disease. Browning that starts at the leaf margins and works inward typically indicates environmental stress rather than disease.

Timing matters. Discoloration appearing in late spring or early summer is more likely disease-related, while mid- to late-summer browning is often drought or heat stress. If your tree is losing leaves entirely during summer, see our dedicated guide on summer leaf loss.

Nutrient Deficiencies

Iron Chlorosis

Iron chlorosis is extremely common in areas with alkaline soils, particularly across the upper Midwest, Great Plains, and parts of the western United States where soil pH exceeds 7.0. The hallmark symptom is yellow leaves with prominently green veins, creating a striking contrast. Affected trees include red maple, pin oak, river birch, and many ornamental species. In severe cases, leaves may turn nearly white and develop brown necrotic patches along the margins.

Nitrogen Deficiency

Nitrogen-deficient trees produce uniformly pale green to yellow foliage, with older leaves affected first. Overall growth is stunted, and the tree may produce fewer, smaller leaves than normal. Nitrogen deficiency is common in sandy soils, newly planted trees, and trees competing with heavy turf grass for nutrients. A soil test confirming low nitrogen levels justifies deep root fertilization treatment.

Manganese Deficiency

Manganese deficiency produces interveinal chlorosis similar to iron chlorosis but tends to affect older leaves rather than new growth. Red maples are particularly susceptible. Like iron deficiency, manganese problems are worsened by high soil pH. Trunk injections of manganese sulfate provide rapid correction, while long-term management requires soil acidification.

Overwatering vs. Underwatering

Both too much and too little water cause leaf discoloration, but the patterns differ. Underwatered trees show browning at the leaf edges (scorch) that progresses inward, with leaves curling or becoming crispy. The tree may wilt during the hottest part of the day but partially recover overnight. Soil around the root zone feels dry several inches below the surface.

Overwatered trees display generalized yellowing, often starting with the lower canopy. Leaves may wilt even though the soil is wet, which confuses many homeowners into adding more water. The soil may smell sour or anaerobic. Prolonged overwatering leads to root rot, which causes progressive decline and eventual death. This is especially problematic in clay soils or areas with poor drainage.

The fix for underwatering is deep, infrequent irrigation at the drip line, allowing water to soak 12 to 18 inches into the soil. For overwatered trees, stop all supplemental watering, improve drainage if possible, and let the soil dry out between natural rainfall events.

Disease Causes of Leaf Discoloration

Anthracnose

Anthracnose is a group of fungal diseases that cause brown, irregular blotches on leaves, often following the leaf veins. It is most severe during cool, wet spring weather and commonly affects sycamore, oak, maple, ash, and dogwood. While it looks alarming, anthracnose rarely kills mature trees. Severely affected trees may drop their leaves and produce a second flush of foliage. Fungicide treatments are available for high-value trees. Learn more on our anthracnose page.

Leaf Spot Diseases

Various fungi cause circular or irregular spots on leaves, ranging from tiny dots to large necrotic patches. Common leaf spot diseases include tar spot on maples (black raised spots), Septoria leaf spot, and Phyllosticta leaf spot. Most leaf spot diseases are cosmetic and do not threaten tree health, but severe repeated infections can weaken a tree over multiple seasons. Raking and disposing of infected fallen leaves reduces reinfection pressure. Browse our leaf spot diseases database.

Leaf Scorch (Bacterial or Environmental)

Bacterial leaf scorch, caused by Xylella fastidiosa, produces browning at leaf margins that is bordered by a yellow or reddish band. It affects oaks, elms, sycamores, and other species, with symptoms worsening each year. Unlike environmental scorch from drought or wind, bacterial leaf scorch is progressive and currently has no cure, though antibiotic trunk injections can temporarily reduce symptoms. Environmental scorch, by contrast, is a one-time response to heat or drought that resolves when conditions improve.

When Discoloration Is Normal

Several types of leaf discoloration are completely normal and require no treatment. Fall color change from September through November is the most obvious example. Inner needle drop on evergreens in autumn, where the oldest two- to three-year-old needles turn yellow or brown, is a natural process. Some tree species like river birch, sycamore, and cottonwood regularly drop a small number of yellow leaves throughout summer without any underlying health problem.

Newly transplanted trees often show leaf yellowing and drop in their first one to two years as they establish their root systems. This transplant shock is normal as long as the tree produces healthy new growth each spring. Young leaves on some species emerge reddish or bronze before turning green, which is also normal development, not a sign of disease.

Frequently Asked Questions